EU rules have rendered Britain powerless to refuse entry to terror suspects and those with a criminal record, Michael Gove has claimed. The Justice Secretary's comments come against a backdrop of rising blue-on-blue attacks as the Vote Leave campaign gains ground in the opinion polls and immigration takes centre stage.

"As Justice Secretary, I have experienced the frustration at our inability to refuse entry to those with a criminal record and even some who are suspected of terrorist links," Gove wrote in an essay on a Brexit. If British voters choose to leave the EU, Gove said the government would pass "emergency measures to curb the baleful influence" of the European Court of Justice (ECJ) within days.

In comments that are bound to anger Number 10, Gove said the only way David Cameron can fulfil the Conservative party's election promise to reduce net migration to the tens of thousands is by leaving the EU. Speaking during the campaign trail on 1 June, Gove said: "The only way he can fulfil that pledge is by leaving the EU. He's the Prime Minister who sets policy, he will set policy on 23 June but we just want to liberate him to be able to fulfil the manifesto pledge we all stood on.

"It is straightforwardly the case that we cannot control our borders in the European Union," he added.

Tension mounts in Tory ranks

As Tory infighting over the EU referendum escalates, Chancellor George Osborne accused the Leave camp of turning a blind eye to the economic consequences of a Brexit. In an open letter with his Labour predecessor, Alistair Darling, the pair said: "Vote Leave, you are coming forward with uncosted and unworkable proposals that would damage our country by taking us out of the single market upon which so many jobs depend.

"It is simply not good enough to pretend to the British people that they can vote leave and there would not be profound and negative economic consequences that would affect them and their families."

Global institutions and Britain's international partners including the US, fellow EU Member States, the International Monetary Fund (IMF), the Organization for Economic Cooperation and Development (OECD) and a string of business have all warned against a Brexit, citing the economic consequences that could follow. Even celebrities, academics and leading figures from science, sport and the arts have all urged British voters to stay in the EU.

In a demand for answers "to avoid suspicion that you have no economic plan and are just making it up as you go along," Osborne and Darling ask Vote Leave to address a series of "basic economic questions" should voters opt for a Brexit.

They include clarification on the UK's trading relationship with the EU, guarantees over the imposition of new tariffs on goods, how long negotiations for trade deals with 53 countries as a result of Britain's EU membership would take and assurances that no jobs will be lost as a result of leaving.

Despite getting off to a stronger start, Remain appears to have lost momentum as the prime minister prepares to make the case for staying in the EU in the first major broadcast event of the referendum campaign tonight (2 June). The Leave campaign currently has 52% support, four points ahead of Remain on 48%, according to an ICM poll for the Guardian.

The survey of 2,052 people revealed that 58% of respondents would be unhappy if current levels of migration were to continue, while 67% believe it has put a strain on housing.

Cameron will take centre stage on Sky News tonight (2 June) at 8.00pm BST, where he will be interviewed by the Sky News' political editor, Faisal Islam before facing questions from the audience. Gove will face the same test a day later on 3 June.